It is known to perform regeneration of activated coal or activated coke by the thermal process in which, for example, activated coke is contacted with a heat carrier medium which is at a temperature of more than 500.degree. C. as described in DE-PS No. 1 719 554. The spent activated coke and the hot sand are fed separately to a desorber. The desorber is equipped with means to ensure good mixing of the two material streams. This method makes use of the phenomenon that gas is liberated during desorption, said gas contributing to the formation of an autogenous fluidized bed in the mixing zone. The means to ensure good mixing are stationary, not mobile. Consequently, optimum mixing and utilization of the heat carrier medium can be achieved under design conditions only.
At part-load--referred to the hourly throughput of activated coke--an irregular distribution of activated coke and hot sand might be encountered. Therefore, the flow rate of recycle sand will generally achieve the process requirements under part-load conditions.
Further known measures, such as the installation of weirs beneath the concentric feed pipes according to OS No. 25 39 266 do not reduce the segregating effect to any appreciable extent and are not fully effective under part-load conditions or require an increased sand flow rate. During their downward flow, the activated coke particles are more and more heated by the surrounding sand, but are at the same time increasingly encapsulated by the sand because the bulk density above the particles rises with increasing depth. Louver-type circumferential guide vanes provide additional gas space, but require enlargement of the desorber.